As the Autumn Statement was not a Budget, detailed publications that would normally emerge as the Chancellor sat down have taken time to appear. For example, HMRC projections of how many more capital gains tax (CGT) payers there would be because of the much-reduced annual exemption (another 570,000 by 2024/25) did not appear until the Monday after the Autumn Statement, missing the weekend personal finance pages.

One even later arrival – three weeks after the Autumn Statement – was an HMRC bulletin on the fuel benefit charge for company cars in 2023/24. For some years the basis has been an increase in line with September annual CPI inflation (published in mid-October), so there was no evident reason for HMRC’s procrastination. The number that was eventually revealed was the current figure, increased by 10.1%, as expected.

That means for 2023/24 if you have ‘free’ fuel, its taxable value will be assessed by multiplying £27,800 by your car’s percentage scale charge. For example, if you have a petrol-engine car with CO₂ emissions of 130–134 g/km, your scale charge is 31% and £8,618 (£27,800 x 31%) will be added to your income for tax purposes. That is an extra £3,447 going to the Exchequer if you are a 40% taxpayer.

At this point you are probably wondering how far £3,447 of petrol would take you. Assuming a price of £1.60 a litre and 40 miles per gallon the answer is about 19,000 miles. In 2019, before the pandemic disrupted travel, the average car covered 7,400 miles a year. If that figure still applies – and it is probably less because of increased working from home – then the ‘free’ fuel break-even point is more than 250% of typical use.

Not all benefits are so harshly taxed – electric cars can be an attractive option – but the large cost of ‘free’ fuel is a reminder that when it comes to anything financial, ‘free’ is a word to be treated with great caution.

Note: Tax treatment varies according to individual circumstances and is subject to change. The Financial Conduct Authority does not regulate tax advice.